Revolutionary class consciousness is a fundamental aspect of the proletariat that not every working class has. If a working class has no consciousness and no revolutionary potential, then it is not a proper proletariat even if it performs wage labor.

As I understand, the proletariat is not only a wage-slave but also a producer of commodities. In a footnote on the first volume of Capital, Marx writes:

Our “prolétarian” is economically none other than the wage labourer, who produces and increases capital, and is thrown out on the streets, as soon as he is superfluous for the needs of aggrandisement of “Monsieur capital,” as Pecqueur calls this person.

I cannot confirm that every time Marx refers to the proletariat he means this. But this definition is extremely important. In the whole book of Capital, Marx is analyzing how value is produced, and how it is extracted by the bourgeoisie to turn into profit.

Under this definition of proletariat, the revolutionary potential of this class becomes more clear: they are the producers of everything that is consumed, even by the bourgeoisie, therefore, they are in a better position to bargain, protest and organize a general strike which is the ultimate weapon of the working class.

The US has proletarians, irrespective of the color of the skin. But the bulk of everything that is consumed by US citizens is actually produced by the proletarians in the Global South.